Such torque motors are known from practice in various embodiments and are used primarily as a direct drive in rotary tables or as a pivot axis of machining centers. They are also used in rotary machines, plastic injection molding machines, and wood processing machines and also in robotics, but also in special applications such as computer tomography and magnetic resonance tomography equipment.
In principle, torque motors work the same as normal synchronous motors. Usually the permanent magnets are glued on the inner surface of a drum that forms the rotor and that serves as the drive. The stator consists of a plurality of coils that are incorporated in an iron matrix. These coils are wye-connected and are supplied with 3-phase AC current. The frequency determines the rotation speed.
Due to the relatively high number of poles, high torque can be achieved at low rotation speeds. Jamming is minimized as a result of the particular arrangement of the permanent magnets. Since the magnets are coupled directly to the elements to be driven, there is no play between tooth flanks rubbing against each other.
In conjunction with prestressed roller bearings, this combination exhibits absolutely no play. Depending on the measurement system used, the stiffness of the drive can also be drastically increased, i.e. greater power and precision. Furthermore, the angular velocity and angular acceleration values can be considerably improved.
Particularly in the case of computer tomography and magnetic resonance tomography equipment, the rotor—which is then usually designed as a hollow shaft—has a large diameter and a corresponding weight, which places particular demands on the bearing.